The rain and storm water filtration systems discussed herein relate to filtration systems that employ screens to filter debris and other unwanted material from water streams and, more specifically, to filtration systems having a Coanda screen for filtering water streams.
Rainwater downspouts, curbside storm water runoff collectors, and similar water conduits share a common purpose: removal of water from where it is undesired, be it the roof of a building, a city street, a storm basin, or the like. All such conduits allow a volume of water to pass therethrough. Leaf litter, sand, dirt, grit, and other debris can accumulate within such conduits and clog them, rendering them ineffective. Equally bad, the poor design of many water conduits allows debris to pass through to downstream channels and, ultimately, the ocean, with a consequent negative environmental impact.
Not surprisingly, much effort and money has been spent devising ways to avoid clogged water conduits and contaminated water streams. Patents have been granted for inventions designed to filter water at curbside storm drains (U.S. Pat. No. 6,231,758 to Morris et al.), to treat water in a horizontal passageway (U.S. Pat. No. 6,190,545 to Williamson), to create temporary stream filtration systems (U.S. Pat. No. 4,297,219 to Kirk et al.), to remove downspout debris (U.S. Pat. No. 5,985,158 to Tiderington), and to shield rain gutters on the eaves of a building (U.S. Pat. No. 4,435,925 to Jefferys).
However, with respect to downspouts and storm water systems, the prior art has several shortcomings. Among other things, it is difficult to devise a system that both operates under high flow and effectively filters out small particulate matter and other debris. This is because a filter element that accommodates large flow must also be designed with large spacing to suit the large flow. However, large spacing allows medium to small particulates and waste to pass through unfiltered. Conversely, a filter element designed to trap small particulate matter typically obstructs flow. An ideal water runoff filter would be both capable of passing high flow therethrough and removing small waste and debris.
Accordingly, there remains a need for a filter system for removing debris from a water stream using a filter element that is amenable to high volume flow, capable of removing or trapping waste the size of or even smaller than the size of the gap used for the filter and, preferably, self-cleaning.
The present invention integrates a Coanda screen (sometimes called xe2x80x9cCoanda-effectxe2x80x9d screen) into water collection systems such as downspouts, storm runoff collectors, sewer drains, and similar conduits and receptacles. An exemplary embodiment includes retrofitting an existing downspout section (or customizing a new downspout section) with a Coanda screen to provide a downspout with a highly efficient filter for removing debris from a stream of water. Depending on the water flow rate and the size of the debris encountered, different screen sizes and different screen mounting angles maybe selected to accommodate the same. Filtered water can pass through the screen, while debris is retained by the Coanda screen and then collected in an optional retaining basket.
In another embodiment, a curbside inlet to a storm drain is fitted with a Coanda screen. The screen is mounted between a raw inlet basin and an outlet basin. Filtered water is allowed to pass over the screen and then fall through the screen into the outlet basin, which then flows onward via an outlet pipe. Captured debris and waste are allowed to fall into a retention basin. To remove waste and debris more effectively, a retaining basket is used. When full, the basket can be lifted out of the curbside inlet and emptied.